Some Apple customers are resorting to extreme measures to keep the wolves from the door, it seems, even selling their beloved iPhones to make a little extra cash.

The number of iPhone 4s being put up for sale by their owners, seemingly in need of some ready cash, has rocketed according to the Guardian.

Mobile phone recycling firm SellMyMobile.com reported a 70 percent increase in enquiries about recycling handsets in the last week of December, with the iPhone 3GS one of the most frequently offered handsets.

Other smartphones such as the Nokia 5800 Xpress Music and the BlackBerry Curve 8520 are also popular among those trading in their handsets for cash, though many of the people doing so are at the end of their contracts and due an upgrade anyway, the paper reports.

There is a roaring trade in iPhone 4 handsets too, though, despite the fact that this model only launched in July 2010 and those recycling them are still well within their contracts. Mazumamobile.com said it had bought between 60 and 100 iPhone 4s every day, bringing the seller an average of £315.

However, as the report points out, you'd probably get a better price for an iPhone 4 on eBay at the moment, with one selling for £430 recently.